Modular circuit board



FIG. 1 is a top perspective view of a modular circuit board, showing my new design;

FIG. 2 is a bottom perspective view thereof;

FIG. 3 is a top view thereof;

FIG. 4 is a bottom view thereof; and,

FIG. 5 is a side view thereof, all other side views being a mirror image thereof.

The broken lines shown in the drawings represent portions of the modular circuit board that form no part of the claimed design. 

CLAIM The ornamental design for a modular circuit board, as shown and described. 